Photo by: John Angelillo
U.S. President Barack Obama speaks to firefighters at the headquarters of Engine Company 54, Ladder Company 4 and Battalion 9, in New York, U.S., on Thursday, May 5, 2011. The firehouse lost 15 members, the single largest loss of life of any firehouse among the 343 firefighters who died during the attack on the World Trade Center on Sept. 11, 2001. Obama will go to New York's "Ground Zero" today, seeking to provide some closure to the worst terrorist attack on U.S. soil now that the world's most hunted terrorist, al-Qaeda leader Osama bin Laden, won't be "walking on this earth again." Photographer: John Angelillo/Pool via Bloomberg

Robert Mueller’s special counsel investigation into Russian meddling in the 2016 election has cost $6.7 million during the first four and a half months of the probe. Click to see past independent counsel investigations guilty of racking up high bills.